I would advice doing 1 unit
Although 2 unit has better scaling, the workload for 1 unit is so much less and the content is very easy! you can practically prepare answers for everything (besides essay!!)
the work is harder for 2 unit!!
i used to do 2 unit and i dropped to 1 unit and my marks have been higher and it was the best decision EVER!!!
you could do a tatical thing like me!!
i selected 2 unit and once all the work for 1 unit was covered i dropped to 1 unit and i was ahead of everyone! it was amazing haha